There are semiconductor devices in which both n-type regions and p-type regions are to be generated on a same side of a semiconductor substrate. For example, manufacturing a next generation of IGBTs (Insulated Gate Bipolar Transistors) can involve properly patterned rear side surfaces of a semiconductor wafer wherein the rear side surface includes p-type regions forming an anode of the IGBT and the rear side also includes n-type regions forming a cathode of an anti-parallel diode. Therein, “patterning” may refer to both an optimized geometry and an optimized doping profile of the p-type and n-type regions.
Such patterned semiconductors have been processed using for example sophisticated masking techniques. For example, an entire area of the surface to be patterned is first doped with a dopant, for example boron or aluminium for forming a p-type doping. Subsequently, areas which shall maintain the p-type doping can be protected with a protection layer such as a dielectric, which protection layer may be patterned using for example masking and photolithography technology. Then, in a second doping process, another dopant, for example phosphorus or arsenic for forming n-type doping, may be doped into the unprotected areas and overcompensate the dopant for forming a p-type doping in these areas.
In US 2009/267200 another manufacturing method for an IGBT using masks is described, in which a p-dopant like boron, boron fluoride or aluminum is deeply implanted through a mask into a first depth into a rear surface of the device and afterwards a first laser anneal is performed, by which anneal the surface is melted down to the first depth and the dopant is completely activated. Due to high mobility during the melting, the dopant is homogeneously distributed within the melted portion. Afterwards, an n-dopant such as phosphorous or arsenic is implanted into a second depth, which is smaller than the first depth in order to form an n-buffer. A second laser anneal is performed, by which the substrate melts to the second depth so that again the n dopant is homogeneously distributed in the melted portion.
However, such patterning of p-type and n-type regions using masking techniques may involve substantial labor and cost.